Hob



Sept. 11, 1951 c, DRADER 2,567,167

' HOB Filed Feb. 4, 1949 5 IN V EN TOR.

Jse Kira/er:

Patented Sept. 11, 1951 UNITED ES PATENT OFFEQE HOB Joseph C. Drader, Detroit ,5 Mich, assignor to Michigan Tool Company, Detroit, Mich.,. a corporation of Michigan ,1 V I ApplicationFebruary 4, 1949, Serial No. 74,513

2 Claims. (cite-105 I cutting elements may easily and conveniently be formed of extremely hard material such, for example, as cemented tungsten carbide.

A principal object of the present invention is to provide a hob structure of the general type referred to above, in which each of the cutting elements, which together form the final hob structure, may be of identical form and shape in order that these elements may be easily and conveniently mass-produced, and so that in the event of breakage it will be possible for relatively u-nskilled workmen to replace a broken. tooth section without the necessity of the precise adjustments which might normally be expected.

Still further the invention contemplates a novel inserted tooth hob structure in which novel and improved means are employed for anchoring the cutting elements in place and at the same time in which means are provided for giving adequate support for the cutting. elements when mounted in position.

Yet another object of the invention consists in the provision of novel means adapted to engage'the axial ends of the respective cutting elements in order that these cutting elements will be accurately and precisely located with respect to each other and with respect to the hob body: 1*

Many other and further objects, advantages and features of the present invention will become apparent from a consideration of the following specification in connection with the accompanying drawing forming a part thereof.

In the drawing:

Figure 1 is an axial end elevational view with parts broken away showing a completely assembled hob of the type to which the present invention relates;

Fig. 2 is a transverse sectional view taken axially through the hob shown in Fig. 1 along the line 2-2 of Fig. 1;

Fig. 3 is a fragmentary view of a portion of the peripheral surface of the hob structure shown in Figs. 1 and 2, taken substantially along the line 3-3 of Fig. 1;

Fig. 4 is an enlarged fragmentary perspective View of a portion of one of the locking caps illustrating in detail the manner in which the locking ings; the hob construction comprises a generally cylindrical body portion l which may be con veniently formed of mild steel and which in the form shown is provided with an axial bore 2 therethrough adapted to receive the arbor (not shown) on which the hob is to be mounted when in use. As is conventional in constructions of 'this general character, this bore 2 is provided with a keyway 3 which serves to lock the hob body in driving relationship to the arbor.

The body portion l of the hob is milled away to provide a plurality of equally circumferentially spaced: axially extending recesses 4, each of which has adjacent thereto an axially extending supportingv rib 5 whichv serves to provide means for supporting and backing up tooth cutting elements 6. Each of these tooth cutting elements 5 is seated in a stepped portion of the recesses A so that its radial position is accurately and precisely controlled.

In accordance with the teachings of the pres ent invention'ea'ch of these tooth cutting ele ments are formed of identical shape, size, length and thickness so that they are completely and entirely interchangeable one with another, and in'the event one becomes broken, a new element may easily and conveniently be substitutedtherefor. Meansare provided for locking these cutting elements in predetermined position with respect to the hob body. The specific locking construction shown contemplates the formation of the cutting elements of wedge shape in cross section wherebythe cutting elements are of progressively increasing thickness from the teeth inwardly to the base thereof. This provides on each cutting element a sloping face I which is adapted to be engaged by a wedge element 8, clearly shown in Fig. 5 of the drawing and illustrated in cross section in Fig. 1 of the drawing. Each wedge element is adapted to be anchored in position by means of a pair of socket screws 9 which may be used to draw the wedge element radially inwardly with respect to the hob.

As is well recognized in the formation of gear cutting hobs, it is necessary that the teeth in each row he slightly axially offset with respect to the teeth in the next adjacent row in order that the ultimate thread of the hob will have the desired lead. It is obvious from the foregoing that for efficient manufacturing operations and to permit mass production of the tooth cutting elements it is essential that all of the cutting elements be identical and interchangeable. Consequently, in order to provide the offset relationship between one cutting element and the next adjacent cutting elements it is necessary to have extremely accurate and precise means for locating the axial position of each of the cutting elements with respect to each other and with respect to the hob body. In order to achieve this result the hob body is provided with a pair of end caps l Which may be locked in position with respect to the hob 'body by means of suitable screws l I. These end caps are each provided with an annular axial face portion which comprises a plurality of locating surfaces 12 clearly illus-' trated in Fig. 4 of the drawing. Each of these locating surfaces [2 lies in a plane perpendicular to the axis of the hob body and each of these end surfaces is adapted to engage the axial end of one of the cutting elements in order that the axial position of each of the cutting elements will be accuratel and. precisely controlled. The amount of the axial offset between one of the locating surfaces l2 and the next adjacent face is determined by the amount of offset required becutting element is provided with the maximum possible support.

- It is readily apparent from the specific embodiment of the invention illustrated in the drawing anddescribed above that man and substantial modifications thereof may be made without departing from the generic spirit and scope of the invention as set forth in the following claims.

What is claimed is:

, 1. A hob for cutting gears including in combination a body having opposite ends, a peripheral surface and an axis parallel thereto, a plurality of toothed cutting elements, each of identical form and length extending generally axially of said body and releasably anchored in position on the peripheral surface of said body, a demountable member anchored to each end of said hob body, said members serving to engage the ends of said toothed cutting elements and locate the same precisely with respect to the hob ibody andwith respect to each other, said demountable members each having a series of progressively axially off-1 set faces, each of, said faces engaging one of said cutting elements and maintaining the teeth there.-

, of in an axially offset relationship to the teeth Q of the adjacent cutting elements, whereby said cutting elements will each lie in a slightly different ,"axial position with respect to said body and wit I respect to each other.

, toothed cutting elements one located in each of tween the teeth of one row and the teeth of the next adjacent row, which in turn depends both on the lead or helix angle of the hob and also, of

course, the number of cutting elements employed.

each located on their respective seats and the wedges 8 are loosely retained in position by means of the set screws 9, at which time the end caps III are mounted in position to accurately position each of the cutting elements in predetermined said recesses, wedge means for locking said cutting elements rigidly in position in said recesses. a cap member for each axial end of said hob, said cap members each having an annular axially extending portion, the axial face of said axiall extending portion comprising a plurality of plane surfaces each lying in a plane perpendicular to the axis of the body portion of said hob, one of said surfaces being provided for each of said longitudinally extending recesses, each of said surfaces being spaced axially from the next adjaaxial position with respect to the hob body. The 1 identical manner as is the case with conventional hobs. It will be apparent that in order to provide adequate backing for the cutting elements the supporting member 5 may be cut to provide teeth therein so that each of the teeth of each cent surface a distance sufiicient to provide the teeth of the hob with the desired lead and means for lockingsaid cap members to said hob body.

-' JOSEPH C. DRADER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,874,536 Irwin Aug. 30, 1932 2,079,995 Hodgkins May 11, 1937 .1 i" 2,207,909 Besaw July 16, 1940 "2,374,528 Emde et al Apr. 24, 1945 FOREIGN PATENTS Number Country Date 593,531 Germany Feb. 28, 1934 

